This invention relates to tufting machines and more particularly to a tufting machine having at least two sliding needle bars with the needles in each bar staggered relative to those in the others, the needle bars being capable of producing stitches at a gauge substantially less than the prior art.
In the production of tufted fabrics a plurality of spaced yarn carrying needles extend transversely across the machine and are reciprocated cyclically to penetrate and insert loops of yarn into a backing material fed longitudinally beneath the needles. The loops are seized by loopers or hooks oscillating below the fabric in timed relationship with the needles as the loopers or hooks cross the needles just above the needle eye. In loop pile machines the loopers point in the direction in which the backing material is being fed, hold the seized loops while the needles are being retracted from the backing, and thereafter move away from the point of seizure to release the loops. In cut pile machines the hooks point in the direction opposite to the direction in which the backing material is being fed so the loops are fed onto the hooks and each hook cooperates with a respective oscillating knife. Since the loops are fed toward the closed end of the hook they cannot be released except by being cut by the respective knife. As the hook rocks away from the point of loop seizure the knife rocks upwardly and cuts the loop. During each penetration of the backing material a row of pile is produced transversely across the backing material. Successive penetrations result in a longitudinal row of pile produced by each needle.
This basic method of tufting limits the aesthetic appearance of tufted fabrics so produced. Thus, the prior art has developed a number of procedures for creating various pattern effects.
One such procedure for patterning is to initiate relative lateral movement between the backing material and the needles to laterally displace longitudinal rows of stitching. One method is to jog or shift the needle bar endwise or laterally across the tufting machine relative to the base material in a step-wise manner in accordance with a pattern, that is the needle bar is slidable in the longitudinal direction thereof. The patented art is abound with disclosures relating thereto, and Ingram U.S. Pat. No. 4,392,440 is exemplary thereof.
The use of a single straight needle bar greatly constrains the versatility of a tufting machine thereby limiting the patterning capabilities. This versatility can be increased by using a laterally shiftable needle bar having staggered needles, i.e., a needle bar wherein adjacent needles are offset in the backing material feed direction. Staggered needle cut pile machines without a shiftable needle bar are illustrated in Crumbliss et al U.S. Pat. No. 3,913,505 and Card U.S. Pat. No. 4,003,321. When a shiftable or sliding needle bar is utilized with staggered needles a temporary crossing-over of adjacent yarns occurs thereby resulting in a greater variety of patterning effects.
It is also known to use two separately slidable back-to-back needle bars each having straight or side-by-side inline needles, i.e., one row of needles in each bar, so as to separate the two rows of needles of a staggered needle bar configuration onto separate needle bars which can be moved independently of one another to bring each needle into cooperative registration with a hook or looper at a given pitch position corresponding to the respective needle bar. This creates a much greater facility to cross one row of yarns and needles over the other row of yarns and needles to provide greater patterning effects.
As explained in the aforesaid Crumbliss et al U.S. Pat. No. 3,913,505 and the aforesaid Card U.S. Pat. No. 4,003,321, in conventional constructions, as used in the context of cut pile, the hooks cooperable with the needles in one row are of a different length than the hooks cooperating with the needles of the other row. That is, the throat length or distance from the bill to the neck of the hooks cooperating with needles of one row are of a different length than those of the hooks cooperating with the needles of the other row. Thus, in the prior art, as exemplified by Card U.S. Pat. No. 4,366,761, when there are two independent slidable needle bars or rows of needles, the hooks cooperating with a given needle bar can only cooperate with the needles in that bar. Thus, it is only possible to move a particular needle laterally by an amount consistent with a multiple of the pitch at which the needles are set on the relevant needle bar. That is to say each needle bar may only be shifted by an amount equal to a whole number multiple of the gauge or spacing of the needles in that needle bar, and which is twice the gauge of the composite needle bar assembly in dual shifting bars staggered needle tufting machines. This limitation manifests itself in a patterned tufted product as a lack of sharpness or definition in the pattern.